This invention relates to a method of mounting a frequency probe in a turbine engine.
Microwave/radio frequency signals have been used to detect, for example, the position of a target component within a turbine engine. A microwave/radio generator produces a signal that is reflected by the target component and processed to detect information such as the position of the target component.
Current methods of instrumentation in a turbine structure require that a hole be drilled in the metal structure to allow the sensor to function. The hole is required to permit communication with a target component. A mechanical connection is required to attach the sensor to the metal structure to prevent leakage. The mechanical connections pose durability issues.
In one example, microwave/radio frequencies are used to detect the clearance of a turbine blade relative to an adjacent housing. The orifice used to accommodate the microwave/radio frequency instrumentation allows air and debris in the turbine gas path to collect within the sensor thereby degrading its performance. The hole also creates a potential pathway for high pressure secondary cooling air used to cool the blade outer air seal to leak through the hole and into the gas path, creating a performance loss.
With prior art methods it is difficult to reliably determine the proximity of the rotating turbine blades relative to the turbine case. What is needed is a method and apparatus for preventing contamination of the sensor and leakage between the cooling path and turbine gas path. What is also needed is a reliable way of establishing an absolute position of the sensor relative to the turbine blades.